(1) Field of the Invention
The present invention relates to a three-dimensional model management system, and more particularly, to a three-dimensional model management system for managing three-dimensional models constituted by multiple parts.
(2) Description of the Related Art
With recent advance in three-dimensional CAD (Computer Aided Design), there has been an increasing tendency to produce necessary drawings, parts lists, etc. from three-dimensional models of products created beforehand on a computer.
Simultaneously, PDM (Product Data Management) has also been spreading in which all data relating to product development is managed in an integrated manner for effective use of data and higher efficiency of design work etc.
Recently, therefore, there is a growing tendency to harmonize three-dimensional CAD with PDM, thereby to make more practical use of data through the course of process from design to manufacture.
Meanwhile, parts defined in CAD and parts defined in PDM are often not in one-to-one correspondence. For example, when drawing a figure by CAD, a dummy part which actually does not exist is sometimes used in order to show the relationship of engagement between parts. Thus, if a parts list is created by PDM based on a three-dimensional model including such a dummy part, a problem arises in that an unnecessary part is also shown.
Also, data created by CAD often has a data structure specific to the CAD. For example, when drawing a part with a plurality of identical portions or segments, it is often the case that a segment is drawn, copied, and modified by rotation etc., to obtain a desired part by finally combining the segments. In such cases, however, since the segments are registered as separate parts, a problem arises in that there is no one-to-one correspondence between the contents of parts list and actual parts. One such specific example is shown in FIG. 35. The illustrated example is constituted by cylindrical parts a and c, and a regular hexahedron b. To draw a three-dimensional model like this by means of CAD, first, the cylindrical part a is drawn as shown in FIG. 36, for example, and the part a is copied and rotated clockwise by 90 degrees to obtain the part b. Then, the parts a and b are joined to the part c to obtain the three-dimensional model shown in FIG. 35. In this case, even if these three parts actually constitute a single part, for example, they are managed by CAD as three separate parts. Consequently, when a parts list is generated, parts that actually do not exist are output.
As another example of drawing a figure by CAD, it is often the case that using a specific surface or the like of a certain part as a reference, another part is made to engage with the part. In such cases, the reference part and the engaged part are often treated as high and, low hierarchical levels, respectively, for convenience’ sake. Since, however, which part is engaged by using which part as a reference part can vary depending upon the designer, there often arises a discrepancy between the hierarchical structure at the stage of design and that of actual parts. In such cases, when the data is displayed in the form of parts list, an unnecessary hierarchical structure is disadvantageously generated. One such specific example is shown in FIG. 37. In this example, hexahedrons A and B are engaged with each other and a bar C is inserted into rectangular holes in the central portions of the hexahedrons, as shown in FIG. 38. When constructing such a three-dimensional model, for example, the hexahedron B is engaged with the hexahedron A as the reference part, and then using the hexahedron A as the reference part, the bar C is inserted. FIG. 39(A) shows a hierarchical structure of the parts derived in this case. Specifically, the hexahedron A is at the highest hierarchical level while the hexahedron B and the bar C are classified as subordinate thereto. In the case where the bar C is inserted using the hexahedron B as the reference part, a hierarchical structure shown in FIG. 39(B) is derived. Thus, the hierarchical structure varies depending upon how the parts are combined, and accordingly, when a parts list is generated, an unnecessary hierarchical structure may possibly be shown, making the structure complicated.
Further, drawings etc. created by CAD sometimes require supervisor's approval. Conventionally, however, to enable such a supervisor to view drawings prepared by CAD, the drawings must be printed out or the necessary CAD software must be installed in the supervisor's terminal, but this consumes time and labor.